The long-range objective of this project is to continue to study the mechanism by which surgical procedures or accidental trauma disrupt the neuroendocrine systems responsible for the control of water and salt balance. Five short-term projects are planned which will consist (1) of determining renal clearance of vasopressin by measuring plasma and urine vasopressin levels during step infusions of synthetic arginine vasopressin, (2) of obtaining more accurate data concerning the decay of vasopressin from plasma following intravenous unit impulse of vasopressin for use in network analysis of vasopressin secretory control system, (3) of creating a non-steady-state response pattern of vasopressin plasma levels in dogs using a computer controlled pump, (4) of developing a sensitive plasma radioimmunoassay for vasopressin to enable faster determination of the non-steady-state vasopressin secretory patterns, and (5) to continue to develop antibodies for the radioimmunoassay of oxytocin. It is hoped that the information gained can be used to further reduce the mortality and morbidity of major surgical procedures and accidental injuries. BIBLIOGRAPHIC REFERENCES: Morgan, M.L., Akatsuka, N., Wilson, M.F., Moran, W.H., Jr., and Sizemore, D.A., Jr.: Renal Blood Flow and Intrarenal Flow Distribution with Steady-State Plasma Vasopressin Levels, Fed. Proc., 34:364 (1975). Akatsuka, N., Morgan, M.L., Wilson, M.F., Moran, W.H., Jr., and Lee, P.: Effect of Arginine Vasopressin (AVP) on Intrarenal Blood Flow Distribution and on Electrolyte Excretion, The Physiologist, 18:118 (1975).